The mammalian brain is anatomically and functionally complex. The rat brain expresses some 30,000 mRNAs which encode the proteins that determine its function: most of these are exclusively expressed in the brain. The distribution of these proteins is what governs the structural and functional properties of the central nervous system. Behavioral studies have localized the anatomical sites for some neuronal functions. Some neurological diseases have primary effects evident within certain brain structures. Our proposed studies will address the issue of the genetic uniqueness, as compared to other rat neuronal structures, of the hippocampus and the cortex. We will prepare cDNA clones of rat cortex and hippocampal mRNAs in 3 ways: cDNA made from total mRNA from each structure, a library enriched by subtractive hybridization, and a Lambdagt11 expression library. We will also prepare polyclonal antisera specific to each region for screening the Lambdagt11 library. It is our first goal to analyze these cDNA clones to determine the genetic uniqueness of the cortex and hippocampus and our second goal to use the region specific cDNA clones to derive the amino acid sequences of region-specific proteins. We will make antisera to synthetic peptides mimicking regions of these putative proteins, and use the antisera to map chemically related cells within the hippocampus and cortex. We will characterize biochemically the proteins using the specific antisera and also determine their subcellular localization. These studies will allow us to judge the molecular heterogeneity of neurons and to use this heterogeneity as a mapping tool as well as providing key information about the molecular function of the hippocampus and cortex. In later parts of this study, the rat proteins will be related to human brain proteins to provide reagents which can be used to study normal and diseased brains.